基于非靶向代谢组学分析副干酪乳杆菌发酵枸杞汁各阶段代谢差异

为研究副干酪乳杆菌NXU-19004发酵对枸杞汁品质特性的影响，采用气相色谱-质谱非靶向代谢组学技术对4 种不同阶段枸杞发酵液差异代谢物进行鉴定分析，结合主成分分析和偏最小二乘判别分析对其进行精确区分。再通过京都基因与基因组百科全书（Kyoto Encyclopedia of Genes and Genomes，KEGG）数据库注释差异代谢物参与的代谢途径，从中筛选出关键代谢物。结果表明，4 种发酵液共检测到63 种非挥发性差异代谢物，其中氨基酸类、有机酸类、酯类等成分在枸杞发酵液中平均相对丰度总体呈上升趋势。多元统计分析结果显示，各样品之间差异显著，均有明显样本聚集区，表明代谢产物可用于甄别发酵阶段。共注释到47 条代谢途径，富集代谢产物较多且显著性高的关键通路有9 条，且多与氨基酸代谢相关，可见发酵阶段对枸杞发酵液中氨基酸类物质的代谢影响最大。进一步确认了关键代谢物为丙氨酸、柠檬烯、苯甲醛、苯甲酸、烟酰胺、烟酸、角鲨烯、脯氨酸、肌氨酸、2-苯基乙酰胺。该研究从代谢组学角度初步揭示了枸杞及其乳酸菌发酵产品的代谢产物差异性以及特征化合物，为进一步研究影响乳酸菌发酵形成差异的因素提供理论依据。

Non-targeted Metabolomics Analysis of Differential Metabolite Profiles of Goji Juice Fermented by Lactobacillus paracasei

In order to study the effect of fermentation by Lactobacillus paracasei NXU-19004 on the quality characteristics of goji juice, non-targeted metabolomics based on gas chromatography-mass spectrometry (GC-MS) was used to identify and analyze the differential metabolites of fermented goji juice samples at four different fermentation times, and principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) were used to distinguish the four samples. Then the metabolic pathways of the differential metabolites were annotated in the KEGG database to identify the key metabolites. The results showed that a total of 63 differential non-volatile metabolites were detected in the four samples. Among them, the average relative abundance of amino acids, organic acids and lipids in fermented goji juice showed an overall increasing trend with fermentation time. The results of multivariate statistical analysis showed that there were significant differences between the samples, and an obvious clustering area was observed for each sample, indicating that the samples can be discriminated based on the differential metabolites. A total of 47 metabolic pathways were identified, and 9 key pathways through which more differential metabolites could be enriched were observed, most of which were involved in amino acid metabolism. It could be concluded that fermentation time had the greatest influence on the metabolism of amino acids in fermented goji juice. It was further confirmed that the key metabolites were alanine, limonene, benzaldehyde, benzoic acid, nicotinamide, niacin, squalene, proline, sarcosine and 2-phenylacetamide. The results of this study provide a theoretical basis for further studies on the factors affecting the formation of differential metabolites in goji juice during lactic acid bacteria fermentation.